DB handler

<?PHP class DB {

private static $_instance = null;
private static $_pdo = false;



private function __construct(){

     $_host = 'localhost';
     $_db   = 'computer_monitor';
     $_user = 'cm_handler';
     $_pass = 'PASSWORD';

     try {
        self::$_pdo = new PDO(
            'mysql:host=' . $_host .
            ';dbname=' . $_db .
            ';charset=UTF8',
            $_user,
            $_pass
        );
    } catch( PDOException $e ){ echo $e->getMessage(); }
}

private static function getInstance(){
    if( !isset( self::$_instance ) ) self::$_instance = new self();
    return self::$_instance;
}



// https://www.owasp.org/index.php/PHP_Security_Cheat_Sheet#PDO_Prepared_Statement_Wrapper
public static function query( $sql ){
    self::getInstance();
    $args = func_get_args();

    if( count( $args ) === 1 ){
        if( !$result = self::$_pdo->query( $sql ) ){
            $error = self::$_pdo->errorInfo();
            trigger_error('Unable to prepare statement: ' . $sql . '<br>Reason: ' . $error[2] );
            return false;
        }
        return $result->fetchAll( PDO::FETCH_ASSOC );

    } else {
        if( !$stmt = self::$_pdo->prepare( $sql ) ){
            $error = self::$_pdo->errorInfo();
            trigger_error('Unable to prepare statement: ' . $sql . '<br>Reason: ' . $error[2] );
            return false;
        }

        array_shift( $args ); //remove $sql from args
        $i = 0;
        foreach( $args as &$v )
            $stmt->bindValue( ++$i, $v, is_int( $v ) ? PDO::PARAM_INT : PDO::PARAM_STR );

        if( !$stmt->execute() ){
            $error = $stmt->errorInfo();
            trigger_error('Unable to prepare statement: ' . $sql . '<br>Reason: ' . $error[2] );
            return false;
        }
        return $stmt->fetchAll( PDO::FETCH_ASSOC );

    }
}

public static function lastID(){
    return self::$_pdo->lastInsertId();
}

} ?>